The present invention relates generally to diesel engine fuel injection and relates more particularly to method and apparatus for shaping the rate of fuel injection
A principal object or the present invention is to provide new and improved method and apparatus in a fuel injector for reducing or regulating the rate or fuel injection during an initial stage of injection.
Another object of tile present invention is to provide new and improved method and apparatus in a fuel injector for injecting an initial reduced charge for pre-injection.
A further object of the present invention is to provide new and improved method and apparatus in a fuel injection for metering fuel during an initial stage or injection.
A further object of the present invention is to provide new and improved method and apparatus in a fuel injection for assisting in maintaining fuel pressure at the injection valve seat until valve closure to reduce or eliminate secondary fuel injection, end or injection fuel dribble and cavitation erosion at the valve seat and adjacent area.
A further object of the present invention is to provide a new and improved two stage fuel injector having a regulated or reduced rate or fuel injection during a first stage of injection. In accordance with the present invention, the two stage fuel injector may employ one or two (or more) valve closure springs. In the two spring embodiment, only one spring is effective when the injector needle valve is closed and as the needle valve is opened to a predetermined intermediate position. Both springs are effective as the needle valve is opened from that intermediate position to its fully open position. In a single spring embodiment, a single spring is effective when the needle valve is closed and as the needle valve is opened to its fully open position. In both versions, during a first stage or needle valve operation, fuel rate shaping is provided in a manner which does not rely on fuel metering between the needle valve and its valve seat and which is substantially insensitive to slight variations in needle valve lift.
A further object of the present invention is to provide a new and improved fuel injector which fulfills one or more or the foregoing objects of the present invention and which can be economically manufactured on a mass production basis.
Other objects of the present invention will be in part obvious and in part pointed out more in detail hereinafter.
A better understanding of the invention will be obtained from the following detailed description and accompanying drawings of preferred embodiments of the present invention.